PC Freezes-CPU Usage Extreamly Low

 I was told in a previous forum that my problem was related to windows.  While on the net, my PC will freeze.  I will then do a ctrl/alt/del to cancel out, and I notice that my CPU usage is almost 0.  Do I have a virus?  I have performed many virus checks and have not come up with one.  I am almost ready to use my recovery CD that came with my system, but I want to make sure that I don't cause further harm to my PC.  I realize that if I use my recovery CD that I will have to save all info to a cd or a diskette. 

Any help on this would be appreciated